An analog/digital conversion circuit (which will be also referred to as an AD conversion circuit hereinafter) that performs conversion from an analog signal into a digital signal (which will be referred to as analog/digital conversion hereinafter) generally has an amplification circuit that executes amplification calculations.
The amplification circuit often uses differential signals to improve signal quality, and in this case, the amplification circuit becomes a differential configuration. When the amplification circuit has the differential configuration, it has a common mode gain, and hence, a common mode voltage which is output from the amplification circuit fluctuates due to fluctuations or the like of the input common mode voltage. A large fluctuation of the common mode voltage exceeds a voltage range where an internal current source appropriately operates in some cases, which may be a cause for errors of amplification calculations.